The microstructures of wires prepared by using the powder-in-tube technique and subsequent hot isostatic pressing were investigated via transmission electron microscopy. A large number of crystalline defects, including small-angle twist, tilt and bend boundaries in which high densities of dislocations resided, were found to form sub-grains within MgB2 grains. It was believed that these defects resulted from particle deformation during the hot isostatic pressing and were effective flux pinning centers that contributed to the high critical current densities of the wires at high temperatures and in high fields.

Defect Structures in MgB2 Wires Introduced by Hot Isostatic Pressing. X.Z.Liao, A.Serquis, Y.T.Zhu, L.Civale, D.L.Hammon, D.E.Peterson, F.M.Mueller, V.F.Nesterenko, Y.Gu: Superconductor Science and Technology, 2003, 16[7], 799-803